Output formats for Tufte-style handouts in html for Rmarkdown. See it in action here http://sachsmc.github.io/tufterhandout.

From CRAN

install.packages("tufterhandout")

Or from Github:

devtools::install_github("tufterhandout", "sachsmc")

When authoring a document in rmarkdown, simply specify the output format in the front-matter:

output: 
    tufterhandout::html_tufte_handout

In html, sidenotes are created with the tag <aside></aside>. You can even put code chunks in aside. Margin figures use the knitr option marginfigure = TRUE and full width figures use the knitr option fig.star = TRUE. Make use of the fig.cap option to specify the figure captions.

See the help files for complete options and see the homepage for an example. Options can be passed via the header:

output: 
    tufterhandout::html_tufte_handout:
        keep_md: true
        theme: cerulean